Various types of surgical procedures may necessitate anastomosis between two tubular tissue segments in order to restore the natural function of the tissue segments. For example, during colon and rectal resection surgery, a diseased or otherwise defective portion of the colon of a patient may be removed, and the colon segments above and below the removed portion may need to be reconnected to restore the natural flow through the colon. Traditionally, the upper and lower colon segments were rejoined by suturing the respective ends of the colon segments to one another. In recent years, surgical staplers have been developed for performing an end-to-end anastomosis between two tubular tissue segments, allowing clinicians to reconnect the tissue segments in a more efficient and reliable manner during a surgical procedure.
Existing surgical staplers for performing an end-to-end anastomosis generally may include an elongated tubular shaft, a handle attached to a proximal end of the tubular shaft, and a head assembly attached to a distal end of the tubular shaft. The head assembly may include an outer shell that contains a mechanism for forming a circular array of staples to connect two tubular tissue segments. For example, a staple guide may be fixedly positioned within the outer shell along a distal end thereof, and a staple pusher may be movably positioned within the outer shell and configured for advancing a plurality of staples through the staple guide. The head assembly also may include a mechanism for coring respective portions of the tissue segments being stapled to one another. For example, a circular knife may be movably positioned within the outer shell and configured for cutting inner portions of the tissue segments within the circular array of staples. The formation of the array of staples and the removal of the inner portions of the tissue segments may be facilitated by an anvil that is removably attached to a trocar of the head assembly. The trocar may be movably positioned within the outer shell and configured to draw an anvil head of the anvil adjacent to the distal end of the outer shell. In this manner, the staples may be advanced through the staple guide, through respective portions of the tissue segments, and against the anvil head to facilitate desired deformation of the staples. Additionally, the circular knife may be advanced through respective portions of the tissue segments and against the anvil head to cut and remove inner portions of the tissue segments within the circular array of staples.
When existing surgical staplers are used to perform an end-to-end anastomosis between two colon segments, the head assembly and a portion of the tubular shaft of the stapler may be inserted through the anus of the patient and advanced through the rectum to the end of the lower color segment, while the handle remains outside of the patient to allow the clinician to control positioning and operation of the stapler. The head assembly generally may be relatively large in order to accommodate the various components for staple formation and for cutting the inner portions of the colon segments being joined. Further, the distal end face of the head assembly may be flat or relatively flat in order to cooperate with the mating portion of the anvil head, resulting in an abrupt edge along the outer circumference of the head assembly. In many instances, it may be challenging for the clinician to insert the head assembly through the anus and the rectum and advance the head assembly to the desired location at the end of the lower colon segment. For example, due to the size and/or shape of the head assembly, it may be difficult to advance the head assembly through the anus and then through the contours of the rectum without snagging on the mucosa folds. In some instances, as the head assembly is advanced to the desired location, the size and/or shape of the head assembly may result in injury to the surrounding anatomy and various complications for the patient. For example, introduction of the head assembly may result in anal sphincter injury, which may lead to loss of voluntary control of bowel function. Additionally, as the head assembly is moved to the desired location, it may engage and cause damage to the internal lining of the colon, which may lead to bleeding or potentially a leak along the respective region of the colon. Finally, in view of the known challenges in advancing the head assembly to the desired location, clinicians often may remove a larger portion of the colon than is truly needed in order to ease insertion and positioning of the head assembly within the patient.
There remains a need for improved surgical staplers and methods of using such staplers to perform an end-to-end anastomosis between two tubular tissue segments, such as colon segments following resection of a portion of the colon. In particular, it would be advantageous to provide a surgical stapler that eases insertion and advancement of a head assembly of the stapler to a desired location for performing the anastomosis, while reducing incidence of injury to the surrounding anatomy and complications for the patient.